Studies of the fundamental chemical behavior of nitrenium ions, which are the ultimate carcinogens derived from aromatic amines, will be undertaken. These will involve: (1) molecular orbital calculations on model systems and nitrenium ions; (2) metagenic assays on modified molecules similar to the non-mutagenic 1-naphthylamine; (3) 0-18 labelling of the o-acetylarylhydroxamic acid derived from the carcinogenic and non-carcinogenic amines in order to study the involvement of ion pairs in the carcinogenic reaction; and (4) study of the rates and products of reaction of the nitrenium ion precursors with various nucleophiles.